There are two differences between designing Custom Tree Houses versus Themed Environments.
1. Themed Environments are usually bigger than Custom Tree House. For instance, a Themed Environment can fill an entire casino, inside and out (ever been to Las Vegas?).
2. Custom Tree Houses are meant to be played on, so there are design restrictions for child safety and 'playability'. Themed Environments, on the other hand, simply create an amazing atmosphere; usually for businesses. Themed Environments give us a little bit more design freedom.
